1. Field of the Invention
The present invention is generally related to a disintegrative core for use in die casting and, more particularly, to a particular structure of a salt core which reduces porosity in a cast metallic object in the vicinity of a cavity formed around the disintegrative core.
2. Description of the Prior Art
Those skilled in the art of die casting are familiar with the use of disintegrative cores, such as salt cores, that are used to define the shape of a cavity within a cast metallic component.
U.S. Pat. No. 3,764,575, which issued to Anderko et al. on Oct. 9, 1973, describes a salt core containing synthetic resin and water-glass as binders. In the manufacture of a casting having a cavity, wherein a water soluble salt core is suspended in a mold, molten material is poured into the mold about the core, the molten material is allowed to harden to the desired casting, and the core is washed away with water to leave a hollow casting.
U.S. Pat. No. 3,801,334, which issued to Dewey on Apr. 2, 1974, describes salt casting mixtures. Alkaline metal nitrates and nitrates are useful as core material for making disposable cores, mandrels and other forms for use in making hollow plastic articles.
U.S. Pat. No. 3,963,818, which issued to Sakoda et al. on Jun. 15, 1976, describes a water soluble core for pressure die casting and process for making the same. The process includes pre-drying a granular water soluble salt having grain size of less than about 1,000 microns so that the moisture content thereof becomes less than 1%, molding under compression the granular water soluble salt into a desired shape and volume at a pressure of between 1.5 to 4 tons per square centimeter, and if necessary, sintering the molded salt at a temperature of between about 100 degrees to 300 degrees centigrade.
U.S. Pat. No. 3,964,534, which issued to Rabinowitz on Jun. 22, 1976, describes a casting method with a vacuum bonded dry sand core. A method for preparing sand cored parts is disclosed which is applicable to certain types of molding techniques where the mold cavity is at least slightly porous, such as a shell molding, green sand molding, and most importantly, the cavityless method of molding.
U.S. Pat. No. 4,361,181, which issued to Wischnack et al. on Nov. 30, 1982, describes a casting core and process for the production thereof. A casting core is intended for the creation of difficultly accessible cavities in castings of aluminum or of one of its alloys, produced from a water soluble salt as base substance and burnt sugar as a binding agent, and a process for the production of such a casting core wherein the base substance is mixed with burnt sugar in aqueous or organic solution, pressed in molds, and baked at elevated temperature.
U.S. Pat. No. 4,446,906, which issued to Ackerman et al. on May 8, 1984, describes a method of making a cast aluminum based engine block. A method of making a die cast aluminum based engine block with a closed deck is disclosed. A core assembly having at least one water soluble alkaline metal salt core member is stationed on a bore die of a die casting assembly for the block.
U.S. Pat. No. 4,875,517, which issued to Donahue et al. on Oct. 24, 1989, discloses a method of producing salt cores for use in die casting. A pattern, identically proportional in configuration to the salt core to be produced, is initially formed from an evaporable foam material. The evaporable foam pattern is positioned in a mold and surrounded with an unbonded flowable material, such as sand. The pattern is contacted with a molten salt and the high temperature of the salt will vaporize the pattern, with the vapor being captured within the interstices of the sand while the molten salt will fill the void created by vaporization of the foam to provide a salt core identical in configuration to the pattern.
U.S. Pat. No. 5,165,464, which issued to Donahue et al. on Nov. 24, 1992, discloses a method of casting hypereutectic aluminum-silicon alloys using a salt core. A method of high pressure casting of hypereutectic aluminum-silicon alloys using a salt core to form wear resistant articles, such as engine blocks, is described. To produce an engine block, one or more solid salt cores are positioned within a metal mold with the space between the cores and the mold defining a die cavity.
U.S. Pat. No. 5,273,098, which issued to Hyndman et al. on Dec. 28, 1993, describes removable cores for metal castings. A method for the manufacture of salt cores is described.
U.S. Pat. No. 5,303,761, which issued to Flessner et al. on Apr. 19, 1994, describes a die casting using casting salt cores. A process of providing a disposable core for use in die casting processes is described. A salt material is molten and cast into a core of a desired configuration under exacting conditions. The fluidity of the molten salt is controlled enabling casting the salt material into a core by die casting methods.
U.S. Pat. No. 5,632,326, which issued to Gough on May 27, 1997, describes a mold and method for the casting of metals and refractory compositions for use therein. A mold for metal casting contains a bonded refractory composition comprising hollow alumina-containing microspheres in which the alumina content is at least 40% by weight.
U.S. Pat. No. 5,803,151, which issued to Carden on Sep. 8, 1998, describes a soluble core method of manufacturing metal cast products. An improved soluble core for die casting metals or metal matrix compositions is formed of a mixture of salt and up to 20% weight of ceramic material blended together to produce a homogenous mixture and compacted under pressure to produce a soluble core having little or no porosity.
U.S. Pat. No. 6,458,297, which issued to Moschini on Oct. 1, 2002, describes a method for producing pressure die cast or injection molded articles using salt cores. A method for producing pressure die cast or injection molded articles having a unit for producing salt grains, a press for forming salt filler cores by compressing the salt grains, a pressure die casting machine for making the said articles by injecting a material in the liquid state into a mold having at least one salt filler core, and a salt removal and washing unit designed to remove the salt filler cores that have been trapped within the articles is described.
U.S. Pat. No. 6,755,238, which issued to Hirokawa on Jun. 29, 2004, describes a disintegrative core for high pressure casting. It discloses a method for manufacturing a disintegrative core for use in high pressure casting. The disintegrative core can be applied where a light metal such as an aluminum alloy or magnesium alloy is subjected to high pressure casting, such as die casting or squeeze casting and is manufactured from a water soluble salt which is high in latent heat and ranges, in melting point, from 280 to 520 degrees centigrade. The salt, alone or in combination with a fine hard powder, is melted and solidified in a core mold. Alternatively, the melt is produced into a fine powder which is then molded into a core mold. The method can be applied for the manufacture of complex shapes of cores.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.